Vinegar Weedkiller vs RoundUp: Testing Head to Head

Over a year ago I wrote a blog post on why I think the internet’s popular vinegar-based weedkillers are BS. I had sort of hoped that they’d go away like just another passing fad, like pogs or Reebok pump sneakers. Every week I see the same old recipes on Facebook and Pinterest, and I wouldn’t mind except that there are people saying that just like with RoundUp the weeds are completely killed and don’t come back. That makes no sense, given the way science and reality work.

I set out to find videos of experiments that would either prove me wrong or back up what I believed and couldn’t find much. Most of what I found were like this video, in which someone mixes up a tank sprayer of each and sloppily sprays some random weeds and comes back in a couple of hours. A couple of hours? Who cares? A weedkiller is pointless if the weeds come right back. How long does vinegar keep weeds down? How long does RoundUp keep weeds down?

Testing Vinegar Weedkillers: The Recipe

Vinegar Weedkiller Experiment Setup

The recipe I referenced in my old blog post, and the one I see the most online, is vinegar mixed with dish soap and Epsom salts. That’s what I decided to test, along with some other formulations. I also tested RoundUp two ways (which sounds like the worst American Chinese food recipe ever).

The Vinegar Vs. RoundUp Test

Video Transcript (But trust me, watch the video):

If you have an internet connection, by now, you’ve seen recipes for alternative weed killers floating around. The one that I have seen the most has been this mixture of vinegar, dish soap, and Epsom salts. The people that are promoting this were saying that this works as well or even better than Roundup which, given how well Roundup works, that was a claim that I thought was a little unbelievable, so I wanted to check that out for sure. My name is Dave Marciniak. I’m a landscape designer and owner of Revolutionary Gardens. You can also follow my blog over at revolutionarygardens.com.

One of the things that’s really important to me is making sure that any information that I share with my readers, with my customers, is all science-based. As a result, I wanted to actually go ahead and test vinegar solutions versus Roundup head to head and see what we came up with. The first step in doing a scientific inquiry is your hypothesis, right? My hypothesis was as follows. I was confident that Roundup or glyphosate, which is the active ingredient in Roundup, would actually do a phenomenal job of knocking weeds back. Roundup or glyphosate is a systemic, which means you spray it on the foliage and it’s actually absorbed through the leaves, goes into the stems, goes into the roots, and kill the entire plant over a short course of time. My fear with the vinegar was that the vinegar solutions would have some minor effect on the plants; it’d have a little bit of burn, knock it back a little bit, but nothing too, too crazy and in the span of a couple weeks, all that weed growth would come right back. That was what I figured would happen and let’s move onto the methodology.

When I came to the idea of how I was going to do this test, I looked for other videos online, another blog post, and what I saw was there was a lot of people that might say, “Hey, I’ve got a tank full of Roundup and I’ve got a tank full of vinegar and we’re just going to go ahead and spray some random fence weeds over here, random fence weeds over there. Few hours later, oh look, that’s dead, that’s dead. Hey, everything’s perfect,” which tells you nothing. When it comes to weeds, it really doesn’t matter what happens two hours from now. It matters what happens two weeks from now, three weeks from now. Are you continually having to go after those weeds or did it take care of it? I wanted to go ahead and test that and give it a really tough real world test.

My front yard at my house here in Culpeper, Virginia, we had a sweet gum tree that we took down a couple years ago. When that tree came down, all of a sudden what was a shady front yard turned into a sunny front yard and the weeds exploded. On my front yard right now is completely rife with all these nasty lawn weeds, centipede grass, all kinds of nasty, gnarly things that you do not want in your yard. I thought, “You know what? This is going to be a great opportunity to test these solutions.” What I did is I decided to make everything as equal and even as possible.

I spray painted two foot by two foot squares and I separated each one of those squares by a two foot gap to make sure that I didn’t have any over-spray or any contamination from one square to the next that might impact my results. I actually was able to do them all in a line, six squares, and I affectionately refer to it as, “My ladder of death.” I then took some AZEK trim lumber, went ahead and cut little squares, took Sharpie, wrote what was being tested in each square on it, and as it turns out, my neighbors commented the other night that they love the fact that I did that, because it was a fun experiment for them and their kids to watch. Hey, it’s not just YouTube. I’m fun in real life, I guess.

From there, what I did was I took all the different solutions and I had one pre-mix, and then everything else I mixed myself in identical tank sprayers that I purchased at Lowe’s. Each square got sprayed and then we did some time intervals and looked to see what the results were.

Square number one got Roundup Pre-Mix. If you walk into your hardware store or big box store, whatever, and you see that little spray bottle of Roundup sitting there on the shelf, kind of looks like a bottle of spray cleaner, same size, sells for $8 to $10, that’s the first thing that I did. The reason why I wanted to do that was that’s something that’s probably the easiest thing for anybody to just go in and pick up. If you’re talking about making weed killing easy and painless and convenient, you walk in, you plunk down a ten spot, you buy something, you’ve got a weed killer. Doesn’t get any easier than that.

Square number two was Roundup made from concentrate. Anybody that uses Roundup more than on tiny, little sidewalk crack weeds once a year, it’s probably the way that you’re going to do it because it’s a heck of a lot more cost-effective than buying the little spray bottle. For $13 you can mix up gallons and gallons versus $10 for that little spray bottle. That was what I did on that.

Square number three was straight vinegar. Again, the solution that I was testing was vinegar mixed with a couple other things, but I’ve never actually used vinegar for weed control. I was curious to see what it would do and I also wanted to see if there was a significant difference between what straight vinegar did versus vinegar mixed with a bunch of other things. That was square number three.

Square number four is vinegar mixed with dish soap. You may have noticed that pretty much any vinegar-based weed killer recommendation you find online has dish soap mixed in with it. The reason for this is that dish soap is what we call a surfactant. A surfactant, simply put, it makes whatever you’re spraying stickier. The idea being that if you were to just spray straight vinegar on something … Think about salad dressing since we’re talking about vinegar, it’s a great analogy. If you just drizzle a cruet full of vinegar on your lettuce, it’s going to run right off. If you mix up vinegar and a little bit of olive oil and then you drizzle it, it’s going to adhere to your lettuce a heck of a lot better, right? It’s the same idea with the surfactant except instead of an oil, in this case it’s a soap. That allows us to have greater contact and greater penetration. There’s definitely going to be a surfactant in the pre-mix Roundup and then also in the Roundup from concentrate but those are actually already mixed in by the company. That is number four, vinegar with dish soap.

Number give is the magic mixture of the internet, which is vinegar and dish soap and Epsom salts. Again, that’s what I was actually testing so I want to make sure, of course, that we had another two foot by two foot square where we’re comparing those results to everything else.

Square number six, I’m not buying that Epsom salts do anything, so square number six was just Epsom salts diluted in two cups of water just because I wanted to see what they ended up doing.

The whole thing behind the Epsom salts real quick is I can see where the theory comes in of mixing some sort of salt in with a weed killer. A lot of weed killers actually do contain salts in them. It’s what helps them kill plants and keep them dead and of course there’s the whole biblical thing of you defeat your enemy and you salt their fields so they can’t grow anything and then their army moves on and they all die. Salt can definitely be an important way of killing plants, weeds, anything, but Epsom salts, first of all, it’s not a huge concentration of salt when you look at the proportions of the mixture. Also, Epsom salts are not like table salt.

Table salt is sodium chloride, NaCl. Epsom salts are magnesium sulfate. The difference being that what it’s doing is it’s boosting the magnesium levels in the soil. I actually use Epsom salts with my tomatoes because tomatoes love magnesium. When I’m prepping my soil in my raised beds for tomatoes every year, I actually mix in Epsom salts and I mix in bone meal. The idea of mixing in something that’s also a soil conditioner, fertilizer, whatever you want to call it, with the stuff that I’m trying to kill with, it didn’t make a whole lot of sense to me. Wanted to test that on its own and see what it ended up doing.

Again, each solution went into an identical container, clearly marked, each square was sprayed and then I waited. The results. At the end of day one, a lot more had happened than I was expecting. Naturally, the pre-mix Roundup square was pretty well fried and that’s what I expected. The pre-mix Roundup has, I’m sure, some additional stuff mixed into it so you’ve got that quick kill thing. Again, you’re buying the little bottle, you want to see results. You want to feel like it’s doing something. The Roundup from concentrate did look like it was starting to get cranking but that takes a little bit longer to get going. That’s been my experience. I wasn’t too surprised by the fact that stuff was starting to look a little damaged, but it certainly wasn’t just schwanked out the way I was expecting.

The vinegar ones surprised the crap out of me because I was honestly not expecting to see as much burning as I did. Again, I’ve never used vinegar as any kind of a weed killer, so I was expecting to see maybe a little bit of stippling burn on the leaves or something like that. Nothing too extensive, but there we go. You can see what it did. Every single one of the vinegar solutions really had a pretty significant effect. Of course, the Epsom salt solution didn’t do a darn thing.

Initial kill is only part of what we’re testing because after all, it doesn’t matter if it kills the weeds today if they come back tomorrow. What I did is I followed up and I wanted to see what they looked like at the end of one week, at the end of ten days, at the end of two weeks, at the end of three weeks. I think the end of three weeks was really the important test and tell to let us know how effective these weed killers are. Let’s take a look at what it looked like at the two week mark.

This is my front yard at the three week mark. Sorry. I’m a mess today. This is ridiculous. Anyhow, the Roundup pre-mix, it was dead initially, it’s mostly dead now. You can see that there’s a couple of new, unique weeds that have popped up in amongst the dead stuff. No big deal. It’s what we expected. For the most part, everything stayed dead so that’s what we expected. The Roundup from concentrate, holy cow. That nuked everything. If you look, that little two foot by two foot square has turned into a four foot diameter hole of death in my front yard. I think it states pretty definitively that if you want something to end up dead and stay dead for a while, Roundup will definitely get it done.

Moving onto the vinegar solutions, you can see that the weeds have really pretty much completely bounced back in every single one of these. That’s a little bit disappointing, but it’s not at all surprising [10:13] because again, Roundup is a systemic. It’s going to kill the entire weed. It’s absorbed in through the leaves, goes to the stems and the roots, and kills the whole thing. Vinegar, all it’s doing is just killing the leaves and that’s it. The Epsom salts, nothing. Nothing but happy green stuff, which is exactly what I expected.

My conclusion is that if you need weeds dead and not coming back, you want them to stay dead, not have to mess with it, Roundup is what you want. Politics and everything else aside, Roundup works better than vinegar. If you’re opposed to the use of Roundup or you want to use vinegar for other reasons, you can certainly do it, but just be aware that you’re going to have to keep using it and keep using it and keep using it. I would have to imagine that if you stay on it and you’re constantly burning the foliage and knocking it back, you will eventually kill that weed, but you’re going to use a lot of vinegar and it’s going to take a lot more time. It’s going to be a lot more effort to do.

That’s the objective part of all this. I’m going to end by giving my opinion on all this here. Here goes. A lot of us that consider ourselves tree huggers and environmentalists, we’ve got real problems with stuff like Roundup. Some of that is due to the parent companies’ policies and track record and history and everything else. I’m not even going to go there at this point. That’s not what this video’s about. There’s also the sense of, “Do I want to be spraying this random thing that comes from a factory in my back yard?” that a lot of people are just not particularly comfortable about. At the end of the day, there’s not a lot of scientific studies out there that I think have shown conclusively that Roundup is dangerous, but by the same point, I could’ve done the same experiment in my back yard, but the dog plays in the back yard and I really didn’t want three weeks of chemicals floating around in the back yard as she’s back there playing so the front yard we decided to test this. At the end of the day, that’s my rant, that’s my choice.

My point being that as environmentalists and as tree huggers and as advocates for what we think are best practices, it’s incumbent on us to be completely transparent and tell the truth, the whole truth, and nothing but the truth. I think we’ve pretty definitely shown that vinegar will kill weeds. I feel good about that. I am blown away at how well vinegar kills weeds but if you’re going to tell me, especially based on what the results that I came up with are that a vinegar weed killer kills them as well as Roundup and better than and they don’t come back, bull. That’s not the case at all. When we put forth misinformation, it hurts the cause.

Let’s say that you have somebody who’s used to using Roundup and they like the efficacy of Roundup and the ease of use and everything else and if you say, “Hey, look, you know what? You don’t need to use Roundup anymore. Use vinegar. It’s better. It’ll work as well,” and you say, “All these garden sites and everything else will tell you that vinegar works better than Roundup,” and this person goes out and they try it and it’s a complete flop and three weeks later their weeds are back, you’ve just lost them. You have lost a potential ally by feeding them the wrong information.

What’s my weed killer recommendation after all is said and done here? If you want a completely no chemical approach, no GMOs, nothing harmful, nothing like that, this is your best right here. Hand weeding. Start early, weed often, stay on top of it. That’s going to be your best bet for weeding and not doing harm to anything by injecting chemicals into your yard or the ecosystem or whatever. If that’s not enough, if you lose control, then you can certainly step it up a notch and start looking at using vinegars or weed torches or boiling water or things like that that are certainly going to be much less intensive and will still help you get the job done.

If it’s completely out of your control or you’ve got invasive vines, you’ve got stuff with a taproot, nothing’s going to work as well as glyphosate or Roundup, or for that matter, at that point you hire a crew to come in and completely gut it out and hammer and mechanically remove the weeds. It’s really all you can do. If you’re 100% opposed to the idea of using Roundup or another chemical herbicide like that, I would say really focus on what behaviors can you institute in yourself to where you can stay on top of those and weed by hand.

I’ve actually gotten a policy in place where when I go out, I cook with charcoal. That’s how I like to grill. When I start that starter, I know that from the time I light that newspaper inside the chimney starter, I’ve got a good twenty-five, thirty-five minutes until I’m ready to dump those coals. Every time I grill, that’s twenty-five, thirty-five minutes of weeding or pruning or doing stuff in my yard. That way, that helps me stay on top of it.

It’s like anything else. There’s no easy answer. It’s 2015. I think we’re so used to, “Well, I got a problem so I want to get a spray. I want to get a cream. I want to get a pill I want to get something like that.” The bottom line is it’s nature. Nature’s not set up that way. If you want to control weeds, do it by hand or you’re going to have a much tougher way of doing it.

If you found this video interesting or useful, please go ahead and comment, like it. I’m going to be doing more of these over time so definitely check back. Subscribe to my channel. If you want to learn more about what I do, if you want to read other stuff that I do, you can find me at revolutionarygardens.com. In the meantime, go outside and play. Thanks a lot, guys. I’ll see you later.

20 comments

  1. DC Tropics says:

    This is the part I like the best: “If you want a completely no chemical approach, no GMOs, nothing harmful, nothing like that, this is your best right here. Hand weeding. Start early, weed often, stay on top of it.” In a small garden like my own, there is never any reason to use herbicides of any kind.

  2. Brilliant! A nice and simple way to show the general public how scientific research is done and how evidence is collected. It doesn’t even matter that no statistics could be collected with such a small sample. The conclusions are clear enough.
    What is most important is to show people that misinformation backfires. Instead of convincing people that herbicides are bad, it discredits your arguments. Stick to the truth at all costs. I have been saying this all along and being accused of being a friend of Monsanto by angry and rather irrational people. Good job here.

    • David Marciniak says:

      Thanks Beatriz! It was a lot of fun, and as I alluded to in the video, my neighbors and their kids even got in on watching the results develop.

      I used to manage the grounds crew for a research institute so I know what actually doing this to rigorous scientific standards would look like, but I’m ok with by little quasi-scientific experiment… if it gets people thinking.

      Thanks again for the kind words!

  3. Begonia says:

    Excellent research but you failed to address the type of weeds you were dealing with or the strength of the vinegar. Like you, I found little effect from the household vinegar/soap/epsom salt mixture when compared with RoundUp. However, I am dealing with a weed that defies RU, Chamberbitter. This has become a pernicious pest in the southeast.. Neither RU or the household vinegar/soap had any effect on it but 20% agricultural vinegar takes out the plant and the seeds permanently and within a few hours if sprayed on a warm, sunny day. Chamberbitter seeds stay viable for many years so the more I can fry before they go to seed the better. I carry a small spray bottle to take them out on an individual basis as I see them. This evil weed is not conducive to good old pulling, you take out a huge root ball of soil and you can’t shake the soil off for fear of dropping seeds.

    • Greenhouser says:

      Thanks for addressing the issue of household vinegar versus the more concentrated version. Too often, people think they have analyzed an issue thoroughly when they have not.

    • A. Marina Fournier says:

      Know anyone from whom you can borrow or rent a goat or two for invasive/hard to kill (even with roundup poison)? In CA, they’re used to combat poison oak and Himalayan Blackberry. Have no clue if they’d work on kudzu, though. They eat anything, roots and all.

      Also, milk of nanny goats who’ve eaten poison oak/ivy/sumac can be used to desensitize humans to their toxin, which doesn’t affect the goats any.

  4. A. Marina Fournier says:

    Thank you for demonstrating how each “formula” affects the weeds.
    For any number of reasons, I won’t use Roundup. I was using a clove-oil formula, but it got pulled off the market–hadn’t heard about its carcinogenic components–but it sure smelled a lot better than the piperidine-based products (I can’t stand peppers of any kind).

    So, I don’t need 20% vinegar (and how would I make it?), but the usual 7% should work? The dog won’t mind too much, but how do our little helpers fare–you know, the little slaveys that fly, ooze, pollinate, turn over and enrich the soil, and eat pests?

    I don’t mind spraying bits and pieces over and over again–backyard full of weeds and nothing else living–until I can get the blasted thing roto-tilled, get de-construction rubble out, and level the entire yard, and prepare it for an herb lawn.

    I use limonene products for cleaning, not weed control. I was sent here via Garden Rant–great recommend!

    • David Marciniak says:

      Vinegar can cause contact burns for some critters so it’s worth considering. On the Garden Professors blog they mentioned in one post that a frog (or toad) got zapped while spraying vinegar. May have been the more concentrated vinegar but I don’t actually recall, and I’m doing the “Sunday morning check email and blog comments while my wife isn’t looking” so looking could get me in trouble 🙂

      Sounds like you have a great project in the works, glad you found the blog!

  5. Anne says:

    Good stuff, science. A whole lot better than viral internet anecdotes.

    You didn’t mention smothering weeds en masse by covering them with plastic. (Most people don’t want to kill huge parts of their lawns or gardens, I get it!) I had no luck with a roundup/brush-be-gone combination for poison ivy (or grapevine, or out-of-control Norway maples). I have resorted to plastic, for months, and while it looks like hell, I might actually be free of some of these plants. (My poison ivy et al behaved like the vinegar-stricken weeds in your experiment. It took more than 3 weeks for them to return, but they all returned.)

    Thanks for this blog! I’m checking it out!

    • David Marciniak says:

      thanks Anne! I’ve never actually tried solarizing weeds. I was considering doing it in the backyard where my patio is going (doesn’t matter if I nuke the soil micro-organisms if there’s going to be a patio overhead) but it’s right in the middle between the back steps and the lower yard. My dog is a spastic idiot and I guarantee she’d refuse to walk across the plastic. So… not this time. Glad it’s worked for you though!

  6. Lally says:

    Round up causes cancer. Nothing tree huggy about it, it causes cancer. C.a.n.c.e.r. I will spray vinegar weekly, I will hand weed vast amounts of lawn, but I will not contribute to skyrocketing cancer rates under any circumstance. So, there ya go.

  7. tslate says:

    Nothing works for everything, however, Roundup will kill you if you ingest it, vinegar won’t unless you drown yourself in it. It’s always great to prove the weenies wrong, good for the ego. I’d rather use something non-invasive with results that are moderate than put that toxic garbage into the world. Monsanto(Bayer) is no ones friend and destroyed alot of farmers livelihoods. Creating a seed that dies at the end of the season is just for intentions that are less than worthy. You can believe all the rhetoric out of their mouths if you want but some things cross the line too far.

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